1. Field of the invention.
The present invention relates generally to ambient air pollution processing and more specifically to purifying exhaust emissions along highway by motor vehicles utilizing such highways.
2. Description of the Prior Art
Catalytic converters have been utilized in closed loop systems where the catalytic converter is disposed in the exhaust path to process pollutants generated by the motor vehicle internal combustion engine. The temperatures of the exhaust gases has generally been high enough (e.g. in the range of 400 to 600 degrees C. to at high power operation e.g. 900 degrees C.) to provide for satisfactory operation of the present 3 way catalytic converters in some instances supplemented during engine warm up (when exhaust temperatures are too low) by electrical heating of the catalysts.
Location of catalytic conversion material such closed loop systems in a high temperature region is shown in my U.S. Pat. No. 3,788,284 where the catalyst is distributed in the exhaust system, more particularly over a portion of the inner wall of the exhaust manifold.
It is accordingly an object of the present invention to provide open loop processing of outside ambient air.
It is a further object of the invention to provide ambient air processing utilizing waste heat from a motor vehicle.
It is yet another object of the present invention to utilize duct controlled air flow over a high temperature exhaust system of a motor vehicle to heat ambient air so that lift off temperatures of catalysts can be achieved.
A primary objective of the system is the utilization of heat from an internal combustion engine to heat catalysts for ambient air processing without compromising engine performance.
It is recognized that the temperature of exhaust gas in a spark-ignition engine can vary from to 400 degrees C. during idle to about 900 degrees C. at high power operation. The most common range is 400 to 600 degrees C. Catalytic oxidation of CO and hydrocarbons in the exhaust is achievable at temperatures as low as 250 degrees C.
Requirements for adequate processing of ambient air surrounding a motor vehicle are dependent upon 3 parameters:
1. The active material must be distributed over a large surface area so that the mass-transfer characteristics between the gas phase and the active catalyst surface are sufficient to allow close to 100 percent conversion with high catalytic activity.
2. Exposure to temperatures of the order of 400 to 600 degrees C. to permit utilization of a wide range of known catalysts.
3. Controlled volume of ambient air flow over a predetermined catalyst surface area.
Cost and Economic Considerations:
1. Zero cost of operation utilizing waste heat.
2. Minimal cost in system deployment.
The present system and method utilizes exhaust system surface heating of catalysts in a duct to process controlled amounts of ambient air through the duct. Emitted exhaust gases may also be utilized to heat a catalytic converter for ambient air processing.